Device for generating signals by emitting shock waves

ABSTRACT

A device for generating signals constituted by successive but discrete shock waves. A continuous chain of explosive material is exploded along its length. Shock wave emitting portions of the chain are in contact with the medium of propagation while other insulated portions of the chain between the shock wave emitting portions absorb the explosions therein.

ilnited tates Patent Delgendre et al.

[451 Sept. 3, 1974 DEVICE FOR GENERATING SIGNALS BY EMITTING SHOCK WAVES Inventors: Jacques Claude Delgendre, Toulon;

Vincent Louis Guigot; Victor Felix Merchandise, both of La Seyne, all of France Assignee: ETAT FRANCAIS represents par le Ministre dEtat charge de la Defense Nationale-Delegation Ministerielle pour lArmement, Paris, France Filed: Apr. 23, 1973 Appl. No.: 353,574

Foreign Application Priority Data Apr. 25, 1972 France 7214547 US. Cl 1102/1 R, 102/24, 102/27, 102/DIG. 2, 181/.5 XC

Int. Cl. F4211! 3/06 Field of Search 102/1, 20, 2224, 102/27, DIG. 2; 181/.5 XC

[56] References Cited UNITED STATES PATENTS 3,112,699 12/1963 Noddin 102]] 3,228,331 l/l966 Drimmer 3,238,871 3/1966 Lang 3,323,611 6/1967 Blayney 3,460,477 8/1969 Heidemann et a1 102/27 3,687,074 8/1972 Andrews et al l02/D1G. 2

FOREIGN PATENTS OR APPLICATIONS 1,138,654 l/l969 Great Britain lO2/DIG. 2

Primary ExaminerVerlin R. Pendegrass Attorney, Agent, or Firm--Larson, Taylor and Hinds [5 7 ABSTRACT A device for generating signals constituted by successive but discrete shock waves. A continuous chain of explosive material is exploded along its length. Shock wave emitting portions of the chain are in contact with the medium of propagation while other insulated portions of the chain between the shock wave emitting portions absorb the explosions therein.

7 Claims, 4 Drawing Figures PATENTED SEP 3974 3. 832 S49 DEVICE FOR GENERATING SIGN BY 1|; SHOCK WAVES BACKGROUND OF THE INVENTION The present invention relates to a device for generating coded signals which allows transmission of information by shock waves, especially in a submarine environment.

At present, for military purposes or within the scope of oceanographic work, there are various methods for transmission of signals in a submarine environment such as active and passive sonar devices and ultrasonic submarine telephone. These present common difficulties which in some cases are drawbacks. The-signal is relatively long or repetitive, which promotes tracking of the source, and long range can be attained only with use of heavy, bulky apparatus.

The use of small explosive charges to transmit data to submerged submarines has already been used in the course of certain experiments where circumstances (high velocity cavitation phenomena) have prevented the use of a submarine telephone.

But information transmitted by the charge is obviously very elementary because it is reduced to a single pulse.

A series of discrete charges exploding at specific times allows emission of a more complicated message, but the total duration of the emission is relatively long because there has to be a delay before explosion of the next charge, until there is sufficient attenuation of all the secondary phenomena (reflected waves, pseudo periods, et.) set up by the former charge. There are therefore limitations in practice to very simple messages which can be expressed by two or three successive explosions.

SUMMARY OF THE INVENTION:

The device of the present invention surmounts the above described disadvantages in the case in which there is to be transmission at a relatively long distance, say several decades of kilometers, of a relatively short message, say several decades of bits. It also offers the advantage of not being directional, and consequently it does not require knowledge of the direction of the receiver.

According to the present invention, a single charge is caused to emit a succession of pulses in sufficient number so that the message may have a length that is of interest, sufiiciently close together so that the totality of the message is received before the advent of secondary phenomena (these being reduced moreover to reflected waves because it is relatively easy to eliminate bubble pulsations by preventing gas diffusion).

The invention therefore relates to a device for the generation of coded signals constituted by shock waves emitted at predetermined times and propagated in a fluid medium, especially submarine, characterized in that the device comprises: a single-continuous chain of explosive material, which chain includes at least two shock wave emitting portions in contact with the medium of propogation to emit in the medium at least two distinct, successive shock waves as the chain is exploded along its length. The shock wave emitting portions are separated from each other by insulated portions of the explosive chain which are insulated in material which absorbs the shock waves of the explosions of those insulated portions. A means is also provided for preventing the escape of gases emitted by the explosive chain as the latter explodes along its length.

According to the invention the device is further characterized in that the separations between the shock wave emitter parts are of dimensions such that the distinct shock waves emitted in succession do not interfere significantly with each other.

A preferred embodiment of the invention is characterized in that the said explosive chain is constituted by a detonating cord contained in a tight metallic sheath that is resistant to the explosion and divided along its length into segments seated in at least one casing lined with material that absorbs the shock waves emitted by the explosion of the said cord, and segments that are in contact with the medium of propagation.

A detonating cord may be located entirely in a casing lined with absorbent material, and it may be joined to at least two explosive elements in contact with the said medium of propagation, disposed so that the shock waves that are emitted do not interfere with each other.

The coding of data to be transmitted may bear on the number and spacing of the shock waves.

In the absence of a suitable receiver, the phenomenon is perceived as a single explosion. It is so brief that it prevents directional tracking and nothing indicates that data have been transmitted.

BRIEF DESCRIPTION OF DRAWINGS The invention will be better understood in the light of the description of specific embodiments which are not limiting, with reference to the attached drawing in which:

FIG. I is a schematic section of a first device according to the present invention, in which the explosive charge is constituted-by a detonating cord disposed along an undulating path.

FIG. 2 is a perspective view of another embodiment in which the detonating cord is disposed along a helical path.

FIG. 3 shows a schematic section of another embodiment of the device of the invention which is especially adaptable for the generation of a binary code.

FIG. 4 is a view in perspective of the device in FIG. 3.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS:

FIG. I shows a device of the invention in which the explosive charge is constituted by a detonating cord 1 in a tight metallic sheath that forms a succession of undulations of equal amplitude. A plane equidistant from the crests of these undulations divides the whole into two parts, one of which parts is enclosed in casing or receptacle 2 lined with absorbent material, and the other of which parts is left in contact with the water. The emitted message is then a succession of identical pluses at equal intervals.

Tests have been run with detonating cords of hexogen (cyclotrimethylene trinitramine) of current manufacture, but the invention is operable with any other explosive substance.

The absorbent material may be foamed polyurethane which is easy to use, or any other alveolar closed-cavity material. Filling with an expanding or swelling material such as glass wool, asbestos silk yields less efficient results, but use of these materials is also possible.

F IG. 2 shows in perspective an example of a practical embodiment of the device in which it is desired to limit the length. The cord is then disposed in a helix whose exact form is to be selected for optimizing of the proportions.

This embodiment offers a very great flexibility in the choice of forms and presents the advantage of being relatively inexpensive. On the other hand, it limits coding possibilities since coding resides solely in the number of pulses emitted, and the maximum of this number is fixed by the construction and can only be reduced by cutting the cord.

It is possible to enhance the complexity of the coding by provision of absorbent cases which could be disposed about a loop of the cord. A binary code can then be used, but this result is attained more practically with another embodiment, which is represented in FIGS. 3 and 4.

According to FIG. 3, a detonating cord 1 is entirely contained in a tight case 2 lined with absorbent material. At regularly spaced points on this cord there are connections on which there can be screwed either solid plugs such as 3, or explosive charges such as 4, the plugs and the charges alone being in contact with the water. The dimensions and the kind of charge are selected so that the respective detonations do not cover each other, account being taken of the length of cord that separates them.

The transmitted message in this case is a succession of pulses or absence of pulses at equal intervals, which allows binary coding.

FIG. 4 shows in perspective an example of an embodiment of the device. Here again a great variety of forms are possible, it being possible for instance to dispose the cord along a spiral or helical path. This embodiment allows transciption of the message to be transmitted with simple tooling a few minutes before use.

Whichever embodiment is used, the initiation, and the safety devices are selected as a function of the same criteria. as for conventional explosive charges.

Moreover, the maximum range allowed by the marine medium for preservation of the form of the signals will be obtained for explosive charges varying in weight from a few tens to several hundreds of grams according to the length of the message, which allows production of light apparatus of little bulk, which can be utilized in particular by aircraft.

Whichever embodiment is used, the length of the message is limited by the difficulties that would cause, in receiving, a partial covering of the direct wave by waves reflected from the bottom or the surface.

A function of conditions of use, this'limit will generally be several tens of bits, and it could only be substantially increased by accepting the complication of receiving facilities and treatment of the signal.

The devices of the invention can be used in military, scientific or industrial applications. In military uses there is essentially transmission of a message to a submerged submarine, thes message transmitter being a surface structure, a submarine, an aircraft or a ground station. The emitter may moreover use a missile or a torpedo to increase the range. In all cases, the omnidirectional character and the range of the transmission allow acceptance of a lesser degree of precision as to the location of the receiver, or even allow intentional transmission rather remote from the receiver to avoid causing its disclosure. Moreover, the briefness of the message is a factor of discretion.

In the scientific and industrial aspects, the main possibilities of application appear in the field of submerged telecommand equipment: automatic-devices for exploration or measurement, valves in petroleum facilites. It would be possible, for example, using a very simply code, to effect telecommand of multiple submerged facilities from a ground station, or from an aircraft wherein only an approximate location is needed.

Although the invention has been described in considerable detail with respect to preferred embodiment thereof, it will be apparent that the invention is capable of numerous modifications and variations apparent to those skilled in the art without departing from the spirit and scope of the invention.

We claim:

1. A device for generating signals constituted by shock waves emitted at predetermined times and propagated in a fluid medium such as a submarine medium or the like, comprising, a single continuous chain of explosive material, said chain including at least two shock wave emitting portions in contact with said medium of propagation to emit in said medium at least two distinct, successive shock waves as the chain is exploded along its length, said shock wave emitting portions being separated by at least one insulated portion of said explosive chain which is insulated from the said medium of propagation by a material which constitutes means for absorbing the shock waves emitted by the explosion of the said insulated portion to a sufiicient extent that the shock waves emitted by the shock wave emitting portions are discemable as discrete shock waves, and means for preventing the escape of gases emitted by the chain in the course of its said explosion along its length which generates the shock waves.

2. A device according to claim 1, wherein the length of said insulated portions separating the shock wave emitting portions are of dimensions such that the discrete shock waves successively emitted by the said shock wave emitting portions, do not interfere with each other.

3. A device according to claim 1, wherein said explosive chain is constituted by a detonating cord contained in a tight metallic sheath that is resistant to explosion and divided along its length into first segments which form said insulated portions and which are located in at least one casing which includes material which absorbs the shock waves emitted by the explosion thereof, and second segments which form said shock emitting portions and which are in contact with the medium of propagation.

4. A device according to claim 3, wherein the said first segments of the detonating cord form an essentially continuous path located entirely in said casing, at least two explosive elements joined to said first segments and extending into contact with said medium of propagation disposed in such a way that the emitted shock waves do not interfere with each other.

5. A device according to claim 4, wherein the said explosive elements are joined to they said detonating cord by connecting elements which are threadedand dis- 7 posed regularly along the said cord in such a way that the shock waves emitted by the explosive elements do not interfere with each other.

6. A device according to claim 3, said chain extending in a continuously undulating path, one part of each undulation being the shock wave emitting portion and located in the medium of propagation, and the other part of each undulation being said insulated portion located in said absorbent medium.

6 being the shock wave emitting portion and located in the medium of propagation, and the other part of each turn being the said insulated portion located in said ab- 7. A device according to claim 3, said chain extend- 5 Sorbent materiaL ing in a helical path, one portion of each helical turn 

1. A device for generating signals constituted by shock waves emitted at predetermined times and propagated in a fluid medium such as a submarine medium or the like, comprising, a single continuous chain of explosive material, said cHain including at least two shock wave emitting portions in contact with said medium of propagation to emit in said medium at least two distinct, successive shock waves as the chain is exploded along its length, said shock wave emitting portions being separated by at least one insulated portion of said explosive chain which is insulated from the said medium of propagation by a material which constitutes means for absorbing the shock waves emitted by the explosion of the said insulated portion to a sufficient extent that the shock waves emitted by the shock wave emitting portions are discernable as discrete shock waves, and means for preventing the escape of gases emitted by the chain in the course of its said explosion along its length which generates the shock waves.
 2. A device according to claim 1, wherein the length of said insulated portions separating the shock wave emitting portions are of dimensions such that the discrete shock waves successively emitted by the said shock wave emitting portions, do not interfere with each other.
 3. A device according to claim 1, wherein said explosive chain is constituted by a detonating cord contained in a tight metallic sheath that is resistant to explosion and divided along its length into first segments which form said insulated portions and which are located in at least one casing which includes material which absorbs the shock waves emitted by the explosion thereof, and second segments which form said shock emitting portions and which are in contact with the medium of propagation.
 4. A device according to claim 3, wherein the said first segments of the detonating cord form an essentially continuous path located entirely in said casing, at least two explosive elements joined to said first segments and extending into contact with said medium of propagation disposed in such a way that the emitted shock waves do not interfere with each other.
 5. A device according to claim 4, wherein the said explosive elements are joined to the said detonating cord by connecting elements which are threaded and disposed regularly along the said cord in such a way that the shock waves emitted by the explosive elements do not interfere with each other.
 6. A device according to claim 3, said chain extending in a continuously undulating path, one part of each undulation being the shock wave emitting portion and located in the medium of propagation, and the other part of each undulation being said insulated portion located in said absorbent medium.
 7. A device according to claim 3, said chain extending in a helical path, one portion of each helical turn being the shock wave emitting portion and located in the medium of propagation, and the other part of each turn being the said insulated portion located in said absorbent material. 